The proxy page is only shown if you choose "Install from Internet" in the first page. If you choose "Download Only" it is never shown. Installer can be downloaded from here: http://download.kde.org/stable/kdewin/installer/kdewin-installer-gui-latest.exe Reproducible: Always
Cannot reproduce with installer version 1.01. The proxy page will be displayed when "skip basic settings" is not checked on the first page independent from the operation type.